U.S. Pat. No. 5,096,950 discloses the co-use of certain NOR (N-alkoxy) hindered amines with a brominated Sb2O3-containing flame retardant in polypropylene.
U.S. Pat. No. 5,393,812 discloses polyolefin compositions which are made flame retardant by a combination of a halogenated hydrocarbyl phosphate or phosphonate ester flame retardant in combination with a alkoxyamine functional hindered amine.
U.S. Pat. No. 5,844,026 discloses polyolefin compositions comprising certain NOR hindered amines and certain conventional flame retardants.
U.S. Pat. No. 6,117,995 discloses that certain N-alkoxy hindered amines may be used as flame retardants for organic polymers.
U.S. Pat. No. 6,271,377 discloses polyolefin compositions that comprise N-hydroxyalkoxy hindered amines and a halogenated flame retardant.
U.S. Pat. No. 6,309,987 and equivalent WO 99/54530 teach polyolefin non-woven flame retardant fabrics that comprise N-alkoxyamines.
A Revolutionary UV Stable Flame Retardant System for Polyolefins—R. Srinivasan, A. Gupta and D. Horsey, Int. Conf. Addit. Polyolefins 1998, 69-83, teaches polyolefins comprising certain NOR hindered amines with halogen and phosphorus containing conventional flame retardants.
Advances in a Revolutionary Flame Retardant System for Polyolefins—R. Srinivasan, B. Rotzinger, Polyolefins 2000, Int. Conf Polyolefins 2000, 571-581, teaches polyolefins comprising certain NOR hindered amines with brominated and phosphorus containing flame retardants.
N. Kaprinidis and R. King, in an abstract posted on the Society of Plastics Engineers website, posted September 2001, discuss the use of NOR hindered amines as flame retardants in polyolefins. The abstract is for a paper submitted to the Polymer Modifiers and Additives Division subsection to be presented at the Polyolefins 2002 conference in Houston, Tex., Feb. 24, 2002. The website is www.PMAD.org.
EP 0792911 A2, discloses polyolefin compositions that comprise alkoxyamine functional hindered amines and tris(trihalogenopentyl) phosphate flame retardants.
WO 99/00450, copending U.S. application Nos. 09/502,239, filed Nov. 3, 1999, and 09/714,717, filed Nov. 16, 2000, disclose the use of certain N-alkoxy hindered amines as flame retardants.
EP 1104766 discloses cross-linked phenoxyphosphazene compounds as flame retardants for synthetic resins.
The flame retardant (FR) market today is comprised of products which function to interfere with the combustion process by chemical and/or physical means. Mechanistically these FRs have been proposed to function during combustion of an article in either the gas phase, the condensed phase or both. The organohalogens are proposed to generate halogen species (e.g. HX) which interferes in the gas phase with free radical organic “fuel” from the polymer substrate. Synergists are proposed to react with HX to form additional chemical species which interfere with combustion in the gas phase, such as reaction of antimony oxide with HX to form antimony halide and water vapor. Antimony compounds such as antimony trioxide also act as radical scavengers forming antimony halides. Thus, they can inhibit the propagation of the fire.
Although antimony compounds are efficient in terms of cost performance, they recently raised concern because of the toxicity of the byproducts which are formed during combustion in the presence of a halogenated flame retardant. Antimony oxides often contain trace amounts of arsenic compounds which are suspected carcinogens. Because of these ecological concerns, there is a movement to replace antimony trioxide in the present commercial flame retardant applications. However, it is very difficult to find an effective synergist which is both environmentally friendly and efficient as far as cost performance is concerned.
Another reason to add flame retardant additives is to prevent dripping during the application of the fire. During combustion, parts of the polymer separate from the matrix in the shape of droplets. Often, the droplets are flaming and impose tremendous danger for fire spread. It is common to add fillers such as talc in large amounts to the polymer, with negative consequences on the mechanical properties. Other fillers sometimes used include calcium carbonate, magnesium carbonate, zinc borate, silicates, silicones, glass fibres, glass bulbs, asbestos, kaolin, mica, barium sulfate, calcium sulfate, metal oxides, hydrates and hydroxides such as zinc oxide, magnesium hydroxide, alumina trihydrate, silica, calcium silicate, magnesium silicate.
It has been found that polymers with good flame retardant properties are prepared when novel compounds are added that comprise at least one sterically hindered nitroxyl, hydroxylamine or hydrocarbyloxyamine moiety and at least one conventional organohalogen or organophosphorus flame retardant moiety. With the use of these novel compounds, antimony compounds and fillers may be largely reduced or replaced. As the instant compounds are active as stabilizers, the polymer compositions of the invention are efficiently protected from the deleterious effects of light, oxygen and/or heat.